The present invention relates to a device for compensating a torque produced by a gyrostatic effect in a movable axle, and more particularly a device for compensating such torque in machine tools or production machines.
Nothing in the following discussion of the state of the art is to be construed as an admission of prior art.
In a machine tool or production machine, the so-called gyrostatic effect that acts on a movable axle of the machine tool or production machine frequently produces a torque that can lead to unacceptable manufacturing tolerances and can mechanically stress the machine components.
For a better understanding of the underlying gyrostatic effect and the associated problems, FIG. 1 shows schematically several exemplary components of a machine that are involved in moving a useful load 1. A motor 3 drives a useful load 1 via a rotating shaft 15 with an angular frequency ωN. The useful load 1 is in the illustrated example represented by a cylindrical workpiece that is machined with the schematically indicated tool 2. The motor 3 is connected by a fixed mechanical link with an axle 4 of the machine that has a disk-shaped upper region. The axle 4 is rotatably supported and is driven by a motor 5, which is capable of rotating the axle 4, for example, by an angle φ. The motor 5 is connected by a fixed mechanical link with a carriage 6 that can move along a direction Y. The carriage 6 is movably supported on two guides 16 and driven by a motor 8. The guides 16 are connected by a fixed mechanical link with another carriage 7 which is movably supported on two guides 17 and driven by a motor 9 along an X-direction. The drive system of the carriage 7, which essentially includes the motor 9, and the drive system of the carriage 6, which essentially includes the motor 8, are only schematically shown for sake of clarity.
The useful load 1, the shaft 15 and the rotating components of the motor 3 (e.g., the rotor of the motor 3) form a so-called useful machine system that rotates with the angular frequency ωN. The rotation of the useful machine system produces a useful angular momentum vector {right arrow over (D)}N shown in FIG. 1 and oriented in the direction of the shaft 15 or the useful load 1, according to the equation (1):{right arrow over (D)}N={right arrow over (J)}N·ωN   (1)wherein    ωN=2*π*f    f is the rotation frequency, and    {right arrow over (J)}N is the moment of inertia of the useful machine system.
It will now be assumed that the useful load 1 is machined first with the tool 2 and thereafter with another tool 17. For this purpose, the axle 4 of the useful machine system is rotated by an angle φ, while the useful machine system still rotates with the angular frequency ωN. The associated temporal change of the useful angular momentum {right arrow over (D)}N produces a useful torque {right arrow over (M)}N according to the equation (2):
                                          M            →                    N                =                              ⅆ                                          D                →                            N                                            ⅆ            t                                              (        2        )            which applies a disturbing force F to the carriage 7 and other machine components via the axle 4. The force F should be compensated by the motor 9 and/or controlled by a position controller of the carriage 7. The useful torque {right arrow over (M)}N produced by the gyrostatic effect therefore mechanically stresses the axle 4 and other machine components, thus adversely affecting the manufacturing tolerances.
It would therefore be desirable and advantageous to provide an improved device for compensating a torque produced by the gyrostatic effect on a movable axle, in particular on a movable axle of a machine tool or production machine.